The first three Star Wars movies that were produced are far better than the others. I say this because the second set of movies to come out are actually supposed to have happened before the events in the other set. Chronologically, only the end of the Star Wars series was worth watching.
The original Star Trek series was corny, but cool. The Star Trek's that followed were better, but only the Picard can be said to have been the best charater over all.
Between the two, I am at an impass. While you have to love Tribbles, the Ewoks had staying power and I don't think the Tribbles could have made a spin-off series of their own. The Picard was hotter than the Skywalker, but the Solo and the Wookie are my personal favorites.
So, give me a Picard, a Solo and a Wookie and I'll say you have the besest space movie cast ever. Throw in Mel Brooks as the nemesis and you'd have yourself a space movie to surpass all others.
